The convergence of the variational expansion (REF ) is as good as for the one-body case. The Gaussian expansion method, indeed, is well documented, as discussed, e.g., in a paper written by some of the best experts of few-body physics, with benchmark calculations in various fields of physics [1]}. In the case of baryons (or multiquarks), care should be taken that all degrees of freedom are incorporated, and this is achieved if one introduces \(2\times 2\)  (\(3\times 3\)  for tetraquarks) matrices which are not restricted to a scalar or diagonal form. For instance, if a system of three equal masses is described with an expansion
\(\sum \gamma _i\,\exp (-a_i(\mathbf {x}^2+\mathbf {y}^2)/2)\) , one will never account for the possibility of internal orbital momenta \(\ell _x=\ell _y>0\) .
